A typical data storage system includes one or more data storage disks coaxially mounted on a hub of a spindle motor. The spindle motor rotates the disks at speeds typically on the order of several thousand revolutions-per-minute. Digital information, representing various types of data, is typically written to and read from the data storage disks by one or more transducers, or read/write heads, which are mounted to an actuator and passed over the surface of the rapidly rotating disks.
The actuator typically includes a plurality of outwardly extending arms with one or more transducers being mounted resiliently or rigidly on the extreme end of the arms. The actuator arms are interleaved into and out of the stack of rotating disks, typically by means of a coil assembly mounted to the actuator. The coil assembly generally interacts with a permanent magnet structure, and the application of current to the coil in one polarity causes the actuator arms and transducers to shift in one direction, while current of the opposite polarity shifts the actuator arms and transducers in an opposite direction.
In a typical digital data storage system, digital data is stored in the form of magnetic transitions on a series of concentric, closely spaced tracks comprising the surface of the magnetizable rigid data storage disks. The tracks are generally divided into a plurality of sectors, with each sector comprising a number of information fields. One of the information fields is typically designated for storing data, while other fields contain sector identification and synchronization information, for example. Data is transferred to, and retrieved from, specified track and sector locations by the transducers being shifted from track to track, typically under the control of a controller. The transducer assembly typically includes a read element and a write element. Other transducer assembly configurations incorporate a single transducer element used to write data to the disks and read data from the disks.
Writing data to a data storage disk generally involves passing a current through the write element of the transducer assembly to produce magnetic lines of flux which magnetize a specific location of the disk surface. Reading data from a specified disk location is typically accomplished by a read element of the transducer assembly sensing the magnetic field or flux lines emanating from the magnetized locations of the disk. As the read element passes over the rotating disk surface, the interaction between the read element and the magnetized locations on the disk surface results in the production of electrical pulses in the read element. The electrical pulses correspond to transitions in the magnetic field.
It is recognized by those skilled in the art that the performance of the spindle motor is critical to providing a high level of data storage system performance and reliability. Normal and accelerated wearing of the spindle motor assembly and, in particular, the spindle bearings, have been associated with a general degradation in data storage system performance. Irregularities in the precision machined surfaces of the spindle motor bearings and deformations in the bearing race, for example, typically result in increased friction within the spindle bearing assembly and accelerated bearing assembly fatigue. Such undesirable changes in the spindle bearing assembly operating condition generally lead to a progressive degradation in spindle motor performance, increased consumption of spindle motor supply current to overcome additional mechanical friction, and, more significantly, a higher probability of temporary or permanent loss of data stored on one or more data storage disks mounted to the hub of the spindle motor.
It is generally considered desirable to detect changes in the performance of the spindle motor early in, and throughout, its service life in order to minimize the probability of intermittent and catastrophic failure of the data storage system. A number of elaborate and typically expensive predictive failure analysis methodologies have been developed in an attempt to detect the existence of failure modes associated with spindle motor bearing assembly deterioration. Many of these prior art methodologies require that the data channel or servo channel be active in order to perform various test routines and to acquire data that, when analyzed, only indirectly indicates the existence or non-existence of a spindle motor failure mechanism.
Additional electronic hardware and control circuitry is often installed into a data storage system in order to support these and other known predictive failure analysis schemes, thus adding to the overall cost and complexity of the system. In small and very small form factor data storage systems, which, in general, are particularly susceptible to spindle bearing fatigue, the relatively compact packaging configuration of such miniaturized systems often preclude employment of a predictive failure analysis scheme that requires installation of additional system components. Moreover, it is believed that none of the conventional spindle motor predictive failure analysis methodologies are capable of detecting the existence of internal data storage system failure modes that adversely affect spindle motor performance yet are not attributable to spindle bearing deterioration or wearout.
There exists in the data storage system manufacturing industry a keenly felt need to provide a spindle motor predictive failure analysis tool that detects degradation in spindle motor performance during the service life of the spindle motor. There exists a further need to provide such a detection tool that requires little or no alteration of the existing configuration of a data storage system, and that minimally impacts the standard operation of the system. The present invention fulfills these and other needs.